This invention relates to the provision of asphaltic concrete in a state or condition suitable for paving application or the like, and particularly to the production of asphaltic concrete in such condition for application from initially solid asphaltic material. In a specific sense, the invention is directed to an asphalt reclamation unit for this purpose.
It is known to heat chunks or other pieces of initially solid, cold asphaltic material (i.e. asphaltic material initially at ambient atmospheric temperature) to provide asphaltic concrete for paving or like application, e.g. for patching. For example, useful asphaltic concrete can be reclaimed in this way from chunks of used asphaltic concrete paving. Desirably, the produced material should be a substantially homogeneous, soft or flowable mass capable of being spread easily and evenly to constitute a patch.
Heretofore, procedures for reclaiming used asphaltic material have involved rapid heating. Difficulties associated with such prior practice have included excessive heating of the material, oxidation of the liquid component thereof, segregation of components, and/or burning. These disadvantages have led to nonhomogenous or otherwise defective products.
Applicant's prior U.S. Pat. Nos. 3,386,435 and 3,577,976 describe units for storing materials such as asphalt at an elevated temperature. In these units, the asphalt is contained within an inner enclosure which is surrounded by an outer enclosure that defines spaces or passages beneath and on all sides of the inner enclosure. Air, heated by an infrared energy source beneath the inner enclosure, flows through these spaces and/or passages to minimize the thermal gradient across the wall of the inner enclosure and thereby to retard heat loss from the contained hot asphalt; the rising heated air is introduced to the top of the inner enclosure through plural horizontally spaced apertures arranged to provide a flow of heated air across the top of the contained asphalt, for further minimizing the heat loss. As will be understood from the cited patents, the purpose of these structures is primarily to maintain the elevated temperature of a charge of asphaltic material supplied to the inner enclosure in initially heated condition, and not to heat an initially cold charge to a suitable temperature for application.
U.S. Pat. No. 2,496,113 describes a heater for melting bituminous material wherein heated gas is passed through an essentially horizontal flue system extending within or beneath the charge of material to be heated and is then conducted upwardly at one end of the heater so as to be directed across the surface of the molten charge. Neither in applicant's prior patents nor the aforementioned U.S. Pat. No. 2,496,113 is there disclosed any provision of passages for conducting heated air or gas upwardly through the body of asphaltic concrete, nor any control means for reclaiming and then maintaining the temperature of the material in a suitable elevated range.
U.S. Pat. No. 3,315,659 describes an open truck for keeping a load of asphalt at an elevated temperature during transportation thereof. Pipe sections are disposed horizontally and vertically within the truck bed for conducting heat through the asphalt. However, there is no disclosure of any means for controlling the temperature of the material, which cannot be properly maintained in an open truck.